1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a semiconductor device having an insulating film whose relative dielectric constant is 3.8 or lower and to a manufacturing method thereof.
2. Description of the Related Art
As a structure of a semiconductor device (semiconductor chip) having multi-interlayer insulating films in which a side face of the interlayer insulating film in the peripheral edge of the semiconductor chip is sealed for improving reliability, that disclosed in the following patent document 1 is an example. In this example, conductors made of the same material as that of wirings or the like are used as seal members.
[Patent Document 1]
Japanese Patent Laid-open No. 2000-277465
For the purpose of further improving the operating speed of a semiconductor device, decrease in wiring resistance, reduction in dielectric constant of an interlayer insulating film with an aim of reducing electrostatic capacitance of a wiring, and so on have been promoted in recent years. Specifically, copper (Cu) is replacing aluminum (Al) as the material of the wiring. As the interlayer insulating film, the adoption of a low dielectric constant insulating film (low-k film) such as a SiO2 film doped with fluorine and a SiO2 film containing an organic component is being promoted in place of the adoption of a simple SiO2 film. Incidentally, an interlayer insulating film whose dielectric constant (capacitance coefficient) k is 3 or less is coming into use in recent years instead of a conventional interlayer insulating film whose dielectric constant k is 4.2.
In a dicing process for cutting out semiconductor chips, caution is required so that mechanical stress of the process does not deteriorate reliability as semiconductor chips. This is important especially in the current circumstances where the adoption of the low dielectric constant insulating film as described above is being promoted as the interlayer insulating film. The low dielectric constant insulating film is obtained by, for example, reduction in material density, exclusion of a dielectric polarization property in the material, or the like. The reduction in material density is achieved by, for example, making the material porous, but such a low dielectric constant insulating film is low in mechanical physical value such as Young's modulus.
Some low dielectric constant insulating film adopts a film structure low in polarity in order to lower a relative dielectric constant in the film. This structure decreases adhesion strength on interfaces of layered films in which low-k films are layered or a low-k film and a different film are layered.
The low mechanical strength of the low dielectric constant insulating film itself and the low adhesion strength on the interfaces of the layered films including the low dielectric constant insulating film may possibly be factors of causing problems in the dicing process, resulting in reliability deterioration as a semiconductor device. Specifically, mechanical stress in the dicing process tends to cause minute peeling and breakage (cracks and burrs) of the interlayer insulating film. When the minute peeling and so on occur in cut surfaces of the interlayer insulating film, the film peeling is made larger in a subsequent assembly process, so that the problem becomes conspicuous.
Under such circumstances, for the purpose of solving the problem in the dicing process, a semiconductor wafer having a trench structure in a dicing part as shown in, for example, the aforesaid patent document 1 is adoptable. It can be thought that this structure also has an effect of enhancing reliability since the sealing of side faces of the interlayer insulating films with the conductors prevents permeation of water and so on into the interlayer insulating films. However, it should be noted that the deterioration of the sealing conductors themselves due to corrosion and so on affects reliability. This is because the deterioration may possibly impair effectiveness as the seal members.